EVAPORATION FROM BARE SOIL 



ished by protective coverings. Stones are effective in this 

 way ; on turning over a large stone in summer time the 

 ground will generally be found moist underneath 1 . Mulching 

 or covering the soil with a layer of farmyard manure, straw, 

 dead leaves, or cocoa-nut fibre is extremely effective, the 

 surface being in this way thoroughly protected from both sun 

 and wind. In the field, valuable results may be obtained by 

 repeated shallow cultivation, by which a few inches of loose 

 soil are permanently maintained at the surface during summer 

 time ; this plan is largely followed in hot climates, and on its 

 use the success of the crop often depends. King has made 

 many experiments on this point, one of which we will describe 

 (Wisconsin 8th Rep., 105). A field which had been ploughed 

 and harrowed in the spring was divided into alternating strips, 

 each 12 ft. wide. One set of strips was rolled on May 14, the 

 intermediate ones were cultivated frequently to a depth of 

 three inches. The percentages of water found at different 

 depths during the summer were as follows : 



TABLE XX 



WATER PER 100 OF DRY SOIL IN SOILS ROLLED OR 

 CULTIVATED (KING) 



1 The beneficial effect of stones in diminishing evaporation from the soil 

 is greatest when the stone, as in the case of flint, is impermeable to water. 



